In general, a motor transmits a rotating force of a rotor to a rotating shaft which drives a load. For example, the rotating shaft of the motor can drive a drum of a washing machine connected thereto, or a fan of a refrigerator connected thereto for supplying cold air to a required space.
Recently, a BLDC (brushless direct current) motor has been widely used since it has no brush to cause almost suppression of noise and to provide extended life span. The rotor in the BLDC motor becomes rotated through an electromagnetic interaction with a stator. So as to perform the electromagnetic interaction, coils, which are made of a material like copper or aluminum, are wound on the stator, and as electric current is applied to the coils, the rotor rotates with respect to the stator.
FIGS. 1 to 3 show a conventional stator for a motor, wherein FIG. 1 is a perspective view showing the conventional stator for a motor, FIG. 2 is a perspective view showing the state wherein a coil drawn from a nozzle of a coil winding machine is wound on the conventional stator for a motor, and FIG. 3 is a conceptual perspective view showing the state wherein the coil drawn from the nozzle of the coil winding machine escapes from the locking projection in the conventional stator for a motor.
Referring to the drawings, a stator 1 for a motor generally includes a stator core having an annular back yoke 11 and a plurality of teeth 12 protruded annularly in a radial direction from the back yoke 11, coils 31, 32 and 33 adapted to be wound on the teeth 12, an insulator 20 adapted to cover the stator core so as to insulate the stator core and the coils 31, 32 and 33 and having supporting ends 21, 22 and 23 formed sequentially to have different heights from one another so as to support the coils 31, 32 and 33 thereon, thereby preventing the coils 31, 32 and 33 from being in contact with one another and locking projections 21a, 21b, 22a, 22b, 23a and 23b formed on both sides or one side of the supporting ends 21, 22 and 23 so as to lock the coils 31, 32 and 33 thereon, thereby preventing the coils 31, 32 and 33 from escaping from the supporting ends 21, 22 and 23. Referring to the drawings, the insulator 20 is classified into an upper insulator 20a and a lower insulator 20b adapted to coupled to the top and underside of the stator core.
In case of an inner rotor type motor, the teeth 12 are extended projected inwardly in a radial direction from an inner circumference of the stator core, and contrarily, in case of an outer rotor type motor, the teeth 12 are extended projected outwardly in a radial direction from an outer circumference of the stator core.
The plurality of coils 31, 32 and 33 are wound on the teeth 12 periodically along one circle of the stator core, and the plurality of coils 31, 32 and 33 are wound alternately within one period. The number of coils 31, 32 and 33 is the same as the number of electric currents supplied to the stator of the motor, and the coils 31, 32 and 33 are wound continuously on the teeth 12 every period corresponding to the constants of the electric currents until the winding on the stator core is finished. In the drawings, the three coils 31, 32 and 33 are wound to supply the electric currents of three phases, and the stator used for the outer rotor motor is shown.
In the meantime, each coil is drawn from one of the teeth 12 disposed within a predetermined period and extended to one of the teeth 12 disposed within the next period. Then, the coil goes to the extended tooth 12. Accordingly, so as to extendedly draw the plurality of coils 31, 32 and 33 from the respective teeth 12 and to go to the respective teeth 12 disposed within the next period, the extended portions of the coils 31, 32 and 33 are supported against the supporting ends 21, 22 and 23 formed to have different heights from one another, such that the extended portions of the coils 31, 32 and 33 are not in contact with one another.
The supporting ends 21, 22 and 23 are formed at the different heights from one another and serve to allow the three coils 31, 32 and 33 to be placed thereon, thereby extending the coils to another teeth 12 therethrough. The supporting ends 21, 22 and 23 have locking projections 21a, 21b, 22a, 22b, 23a and 23b formed at one sides or both sides thereof so as to lock the coils 31, 32 and 33 thereon, thereby preventing the coils 31, 32 and 33 from escaping therefrom.
The coil winding operation wherein the coils 31, 32 and 33 are drawn from the respective teeth 12 and extended to the respective teeth 12 within the next period in the state of being supported by means of the supporting ends 21, 22 and 23 is carried out through a coil winding machine. FIG. 2 shows the winding state of one coil wherein the coil 33 supported on the highest supporting end 23 is drawn from the nozzle N and wound on the corresponding tooth. As shown in FIG. 2, in the coil winding machine for winding the coil 33 on the corresponding tooth, the nozzle N from which the coil 33 is drawn is accessed in vicinity of the teeth 12 and is turn around the corresponding tooth to wind the coil 33 on the corresponding tooth. Next, so as to move the coil 33 to next tooth in the state wherein the coil 33 is supported on the supporting end 23, the nozzle N of the coil winding machine is accessed over the support end 23 disposed between the locking projections 23a and 23b. At this time, if the heights of the locking projections 23a and 23b are low, the coil 33 drawn from the nozzle N is not locked on the locking projections 23a and 23b at both sides of the supporting end 23, thereby escaping from the supporting end 23. FIG. 3 shows the state wherein the coil 33 drawn from the nozzle N is not locked on the locking projections 23a and 23b, thereby escaping from the supporting end 23. The above-mentioned problems are caused when the heights of the locking projections 23a and 23b become low to obtain a compact motor, and especially, they are seriously caused when the height h of each of the locking projections 23a and 23b is smaller than the radius r of the nozzle N.